1. Technical Field
The present invention relates to a recording media separating device that separates the top recording medium from the next-to-top recording media, when a feeding roller and a hopper feed recording media held in a feeding tray. The invention also relates to a recording apparatus having the recording media separating device. Examples of recording apparatuses include printers such as serial printers and line printers, facsimiles, and photocopiers.
2. Related Art
An automatic feeder of a recording apparatus has a separating device for separating multi-fed recording media, i.e., for separating the top recording medium needed for recording from the next-to-top (subsequent) recording media. For example, JP-A-2003-321138 discloses a recording media separating device of a contact-separation type. The recording media separating device has an arm-shaped separating member that pivots about the fulcrum to approach and move away from a feeding roller, and a separating spring that strongly urges the free end of the separating member against the circumference of the feeding roller. The separating member has a sloped surface at the free end. The sloped surface contacts the leading ends of recording media and separates the recording media. This recording media separating device produces less noise than known friction-separation type separating devices, which use friction members.
Ink jet printers, which are exemplary recording apparatuses, have contact-separation type separating devices. More specifically, a fixed contact separator 102 as shown in FIGS. 12 and 13, which is formed integrally with a transportation guide member 101 and serves as a preliminary separator, is located upstream of a retard roller or the like, which serves as a main separator. The fixed contact separator 102 is located at the upstream end of the transportation guide member 101. Recording media (hereinafter also referred to as “sheets of paper”) P slide over the transportation guide member 101. The transportation guide member 101 guides the sheets of paper P. The fixed contact separator 102 includes a rib member projecting from the top surface of the transportation guide member 101.
The fixed contact separator 102 has a contact separation surface 103 at the front surface thereof. The contact separation surface 103 corresponds to the sloped surface of the separating member disclosed in JP-A-2003-321138. The angle of elevation α, i.e., the angle of the contact separation surface 103 with respect to the surface of the transportation guide member 101 serving as the transportation path, is always constant. When multi-fed sheets of paper P contact the contact separation surface 103 of the fixed contact separator 102, the sheets of paper P are separated because of the flexibility of the sheets of paper P and the reactive force exerted by the contact separation surface 103 and produced by sheet-transportation force.
In contact-separation type separating devices, the sheet separation performance largely depends on the angle θ at which the sheets of paper P contact the contact separation surface 103, and the length L between the nip point N and the contact separation surface 103. As shown in FIG. 12, in the case where the number of sheets of paper P urged by the hopper 104, which is a swingable structure having a pivot fulcrum (not shown) on the upper side, is large, the angle θ is large (θ=θ max). Thus, the reactive force exerted by the contact separation surface 103 is large. Accordingly, the sheet separation performance is stabilized. On the other hand, as shown in FIG. 13, in the case where the number of sheets of paper P urged by the hopper 104 decreases to a few, the angle θ decreases (θ=θ min). This reduces the reactive force exerted by the contact separation surface 103, whereby the sheet separation performance becomes insufficient.
Similarly, as shown in FIG. 12, in the case where the number of sheets of paper P urged by the hopper 104 is large, the length L between the nip point N and the contact separation surface 103 is large (L=L max). The strength of the reactive force exerted by the contact separation surface 103 is appropriate in this state. Thus, the sheet separation performance is stabilized. On the other hand, as shown in FIG. 13, in the case where the number of sheets of paper P urged by the hopper 104 decreases to a few, the length L between the nip point N and the contact separation surface 103 decreases (L=L min). This increases the flexibility of the sheets of paper P. As a result, the reactive force exerted by the contact separation surface 103 becomes relatively small, whereby the sheet separation performance becomes insufficient. Variations in the sheet separation performance of the fixed contact separator 102 and the contact-separation type separating device disclosed in JP-A-2003-321138 were caused mainly by variations in the angle θ and/or the length L between the nip point N and the contact separation surface 103 according to the number of sheets of paper P.